My Mark IV hums

[edmiller9999]

I just replaced my power tubes with Mesa 6L6's. Now I'm noticing a hum. It's minor, but definitely there. The hum can be heard even when all three gains, channel levels and master volume are turned OFF. The hum gets louder as I switch from RHY1 to RHY2 to LEAD. Is this an indication of failing pre-amp tubes or are Mark IV's a little noisy by nature?

Thanks.... Ed

 

[willrock]

if you just changed the power amp tubes and problem just came up, you probably had a bad power tube installed.